October 8, 2015: Vertical nystagmus

October 8, 2015

Vertical nystagmus

The clinical finding of pure vertical nystagmus can be a potentially sinister finding and, in conjunction with history and other clinical findings, can help to localize a lesion either to the brainstem or the cerebellum. Since vertical nystagmus implies central dysfunction, it does not improve with visual fixation as might be expected with a peripheral etiology. Vertical nystagmus can be sub-classified as either downbeat or upbeat, which should be distinguished from vertical gaze-evoked nystagmus that is physiological.

Downbeat nystagmus increases with looking downwards and laterally. When spotted, it localizes to a few locations including the craniocervical junction, bilateral flocculus lobes, and bilateral medial longitudinal fasciculi. It is seen in patients with Arnold-Chiari malformation, demyelinating lesions, vascular lesions, and neoplasms in these regions as well as with acute drug intoxication. Upbeat nystagmus is provoked by looking upwards, and while the localization is less defined, it is most often seen in lesions of the superior cerebellar peduncles, caudal medulla, and the cerebellar vermis.